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This is a question in an exercise that I'm having trouble with :

Assume that the switching time (time to store and forward a packet) is 10 microseconds. Will that have a significant impact on the application response time (request response) if the client is located at east coast and the server is located at west coast and assuming that the propagation delay in the links between client and server is approximately two-thirds the speed of light. Justify your answer. (assume east-coast west-coast distance is 5000 km and a speed of light of 200 meters/microsec.)

I've tried to look for relevant sources and I'm lost. I've watched videos and I haven't come any close to solving these questions But from what I've read I understand that you cannot properly determine the actual switching time, so I'm a little confused

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closed as off topic by EEAA, Cheekaleak, Chris S Feb 13 '12 at 19:26

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You should only ask practical, answerable questions based on actual problems that you face. - FAQ –  Zoredache Feb 13 '12 at 19:19
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It's a homework question, Dan, not a real-world problem you're experiencing with real, live networking gear. That's what the FAQ is getting at. –  EEAA Feb 13 '12 at 19:23
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So you are saying that you currently own network equipment hosted in on each coast of the US? Why do you care about the theoretical time it would take for a packet to move between the two locations, just just a quick test and find out what you are actually getting. –  Zoredache Feb 13 '12 at 19:25
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In addition to what @ErikA said, this (extremely simplified theoretical question) is a math question along the lines of "If two trains leave NY and Chicago heading toward each other..." -- To answer the question just do the math: 5000KM = 5000000M. At 200M/µs that means 25000µs RTT. You're adding 10µs for switching (STF), which is 0.04% (10/25000 = 0.0004) -- Significance of that value depends on your application. (Your question assumes a propagation speed of 2/3*C so adjust that 200 number accordingly & recompute.) –  voretaq7 Feb 13 '12 at 19:31
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The question is fatally flawed, because it doesn't mention how much switching is going on to travel those 5,000km. I find it unlikely that there would be just a single switch between those two endpoints. More likely there will be maybe 6 routers (which is substantially slower than a switch) and a few optical repeaters... –  Mark Henderson Feb 13 '12 at 19:32
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1 Answer

Considering your travel time is about 15ms and your switching time is give to be 10μs, the switching time is less than 1/1000 of the overall time. I don't think that would qualify as "significant".

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